1. Field of the Invention
The present invention provides a quick, simple visual continuity testing of fiber optic cables, patch cords, and pigtails (terminated or otherwise). The device serves as a tool for visually testing the continuity of fiber, connector performance, spliced areas, and area of high attenuation. The device may also serve as a visual fault locator and fiber identifier. The invention provides an adaptive interface with the ability to match or connect various fiber optic connector ends and bear fiber ends to a light source, thus permitting a choice of fiber cables to be tested. The invention also provides a multiple light source for testing several fiber cables simultaneously. The invention would have application where the integrity of a fiber optic link is suspect and a visual test would assist a technician in the trouble shooting assessment or allay the concerns of the skeptical/non-technically oriented customer.
2. Prior Art
The simple schematic diagram shown in FIG. 1 consists of an optical transmitter and receiver connected by a length of optical cable in a point-to-point link. The optical transmitter converts electronic signal voltage into optical power which is launched into the fiber by a light emitting diode (LED), laser diode (LD) or laser. At the photo detector point, either a positive-intrinsic- negative (PIN) or avalanche photo diode (APD) capture the light wave pulses for conversion back into electrical current.
A fiber optics link is generally composed of a number of basic components:
a. electro-optical signal transducer-transmitter. PA1 b. optical fiber cable. PA1 c. optical-electrical signal transducer, the receiver. PA1 a. demountable connectors; transmitter-to-fiber, fiber-to-fiber, fiber-to-receiver. PA1 b. branching couplers--for multiple access systems.
Depending on the particular requirements of the system, the link may also include:
The first concern in the design of a fiber optic link is the signal quality. Link design consists basically of two functions: (1) the measure of optical power losses occurring between the light source and the photo detector, and (2) determining band width limitations on data carrying abilities imposed by the transmitter, fiber, and the receiver. If the source emits sufficient power and the receiver is sensitive enough, the system can operate with high losses. How much loss can be tolerated will be determined by the stated minimum requirements of the receiver selected.
The prime causes of optical attenuation in fiber systems are: coupling loss, optical fiber loss, connector loss, and splice loss. In order to minimize power losses, the fiber optic industry has devised a number of devices used to measure power losses through cable connectors and the such.
Optical reflectometry is an advanced technique which allows the optical characteristics of a fiber to a measured given access to just one end. Such equipment launches a short, but extremely powerful pulse of light into the fiber, and then detects the minute returning echo caused by reflections from discontinuities such as breaks within the fiber. By measuring the time interval between the transmitted pulse and the returning echo, the position of major discontinuities can be established to within an accuracy of one or two meters. This extremely sensitive equipment can detect fractures at considerable distances and is even capable of detecting much smaller reflection caused by continuous back scatter along the fiber. Typically, the degree of this back scatter is constant but an exponential decay is observed at the receiver as a result of the attenuation caused by intermediate lengths of fiber. By measuring the rate of this decay, it is possible to make quite reasonable estimates of fiber attenuation, and in particular observe any local increase caused by a severe bend, etc. Alternatively, a hard copy "finger print" of a fiber can be obtained from a chart recorder and used for comparison at a later date (for example, after environmental conditioning).
The sensitivity of this equipment will be appreciated when it is realized that the returning reflection (which is only a maximum of 4% of the incident light, even for a clean fracture) is further attenuated by effectively traveling through the fiber twice (i.e., there and back). Consequently, special techniques have evolved to extract the signal from beneath the level of the background noise.
These optical fiber reflectometers therefore consist of sophisticated computer programmed and programmable features and benefits. They require a trained technician and a sophisticated knowledge of fiber optic technology Further, these types of equipment are extremely expensive.
Other aids devised by the industry to measure losses or attenuation include a Power Meter with or without an optical energy source, and a Visual Fault Locator. The Power Meter reads the source power whether it is transmitted from the transmitting end or artificially supplied. The Visual Fault Locator (VFL) provides a laser source as the optical energy source. It is also very expensive. In addition, the VFL has the additional disadvantage of requiring the operator to view the laser output, causing concern of retinal damage.
As can be seen from the description the current technology on the market the principal of light transmission through optical fibers is highly sophisticated and technical requiring trained personnel. The draw-backs inherent in the current technology on the market include the requirement of expensive equipment to test and trouble-shoot fiber optic linkages. Because of the lack of trained technicians, there is a critical need for a versatile, inexpensive, simple device which has the ability to test the continuity of the majority of optical fibers presently in use today. The present invention fills this need most adequately and appropriately. The present invention can quickly and easily without a doubt visually determine the integrity of a fiber optic link. This inexpensive device encourages the use of current and present technology in trouble-shooting and testing fiber optic links by untrained or newly trained personnel without having to go through expensive and rigorous training.